INVESTIGATIONS ON PARAGUAYAN BATRÀCHIANS. 
217 
at all, may only be arisen through natural selection for the 
purpose of defence.* 
It is an other question, which family this frog can be referred to. 
Mr. Boulenger writes ** on this point : «The genus Eupemphix Stdr. 
(= Engystomops Espada) must, on account of the absence of teeth, be 
referred to the family Bufo iMae, although it is in every other respect 
identificai with Paludicola , to which it stands in the same relation as 
Pseudophryne to Crinia ; this shows that frog-families founded upon the 
presence or absence of teeth are artificial associations.» 
I am quite the same opinion and just for this reason I cannot de¬ 
cide myself to draw this species to the Bufonidae. The organisation of 
Eupemphix Natter eri Stdr. is so highly identificai with that of Paludi - 
coki and even the sternal apparatus (pl. XIII, fig. 9) is exactly of 
the same struetur as in Paludicola signifera Gir. (pl. XIII, fig. 6) 
or in Paludicola fuscomaculata Stdr. (pl. XIII, fig. 7) that it would be 
by no means justifiable to tear so closely allied species into two families. 
The presence or absence of maxillary-teeth does not seem to me an im¬ 
portant character and it appears better to accept that, though most of 
the genera of Cystignathidae are characterized by the presence of maxil¬ 
lary-teeth, there are at the same time a few genera without. 
I fully agree in this respect with Mr. Boulenger, who points out 
several times*** that the establishing of families on the presence or ab¬ 
sence of teeth, as has been invariably the practice since the time of 
Duméril and Bibron, is a very dubious treating. Mr. Boulenger subordi¬ 
nates this character to other points of structure derived from the skele¬ 
ton, as I just have done in the case of Eupemphix. 
8. Leptodactylus mystacinus Burm. 
(pi. XIII, fig. a.) 
Cystigncithus Schomburgkii Günther (nec Troschel, 1848), Cat. Batr. Sal., 
1858, p. 29. 
Cystignathus mystacinus Burmeister, Reise d. La Plata-Staaten, II, 1861, 
p. 532. ^ 
Cystignathus mystaceus Hensel, Arch. f. Naturg., 1867, p. 125. 
Leptodactylus mystacinus Boulenger, Cat. Batr. Sal., 1882, p. 244. 
* Similar lumbar spots, certainly for the same purpose, are on Metopostira 
ocellata Méh. from New Guinea (Természetr. Füz v XXIV, 1901, p. 239, tab. XII, 
fig. 1). 
** Ann. & Mag. Nat. Hist. (6) I, 1888, p. 188. 
*** Firstly in his Catalogue of Batr. Sal., 1882, lastly in his valuable paper 
on Hymenochirus (Ann. & Mag, Nat. Hist., (7) IV, 1899, p. 125). 
